Scarlet Johnson seems like an unfitting choice to me even ignoring whether or not the main character is actually physically Japanese.
Though from what I've seen the older purple haired one seemed more so Japanese while the newer blue haired one seemed white, which is clearly the one they're imitating. I don't get the whole "Well, she has to be Japanese because everything else around her is Japanese" when from what I quickly googled search other characters are clearly at first glance white. I mean, is it really that hard for people to at least misinterpreting that?
I don't even know why I'm even arguing for a film I don't care about whatsoever and have no interest in, but I guess the reason why I joined in is because I don't get why people get so upset about racially ambiguous characters to be confused anyway, especially when the character is a robot anyway. I mean, a Japanese actor would've been better and would've had no controversy. But I still don't think that them being fine with it is not as unjustified as people make it out to be.
People who want Captain America gay is the same people who ship Cap and Bucky.
They don't want him gay for the same of diversity but to justify their ship
It's why people are going insane of the possibility of gay characters in Overwatch, it ain't for diversity I can tell you that.
It's all for the Pharah/Mercy, Zarya/Mei(or D.Va) and/or Junkrat/Roadhog
TBH, the people who want characters for shipping gay for shipping are more logical than the people that want characters gay just so "lolz look dis character iz ghey, iz diverse"". At least then making the character gay actually has a purpose.